Urushiol-induced contact dermatitis (also called Toxicodendron dermatitis and Rhus dermatitis) is produced by the oil urushiol. Urushiol is contained in various plants, including the plants of the genus Toxicodendron, which includes poison ivy, poison oak, and poison sumac, and certain plants in the family Anacardiaceae, such as mango, Rengas tree, Burmese lacquer tree, India marking nut tree, and the shell of the cashew nut. A few unrelated plants, such as Ginkgo biloba, also contain urushiol.
Symptoms of urushiol-induced contact dermatitis include itching, inflammation, oozing, and in severe cases, a burning sensation. The American Academy of Dermatology estimates there are up to 50 million cases of urushiol-induced dermatitis annually in the United States alone, accounting for 10% of all lost-time injuries in the United States Forest Service.
Urushiol-induced contact dermatitis is contracted by contact with a plant or any other object containing urushiol oil. The oil adheres to almost anything with which it comes in contact, such as skin, towels, blankets and clothing. Materials that contact the plant and then contact the skin are common causes of exposure. Normally, it takes about 24 hours for the rash to first appear. For people who have severe reactions, the rash will worsen during the next few days. Histological examination of urushiol-affected skin shows strong evidence of inflammatory cell migration, e.g. activated lymphocytes, mononuclear cells and fibrosis. In severe reactions, a prednisone prescription is necessary to stop skin damage, especially if the eyes are involved. The rash persists typically for one to two weeks but in some cases can last as long as five weeks. At least 25% of people exposed to urushiol will have very strong responses resulting in severe symptoms. Since the skin reaction is an allergic one, some people may mount progressively stronger reactions after repeated exposures.
Primary treatment involves washing exposed skin thoroughly with soap and water as soon as possible after exposure. Because urushiol is an oil, soap or detergent is necessary to remove it. Antihistamines and hydrocortisone creams or, in severe cases, oral antihistamines, can be used to alleviate the symptoms of the rash. Nonprescription diphenhydramine (Benadryl®) is the most commonly used oral antihistamine. Topical formulations containing diphenhydramine are available, but may cause further irritation to the affected skin. In cases of extreme symptoms, steroids such as prednisone or triamcinolone are sometimes administered. Prednisone is the most commonly prescribed systemic treatment, but can cause serious adrenal suppression changes, so it must be taken carefully. If secondary bacterial infection occurs in the affected area, antibiotics may also be necessary.
It is believed that a treatment option that could reduce inflammation and accelerate the healing of urushiol-induced contact dermatitis, such as that exhibited by poison ivy, poison sumac and poison oak, and not have the associated risks of steroids, especially oral steroids, is desirable. Accordingly, it is an object of the instant invention to provide such a treatment option.